The present invention relates to a sealing glass and, particularly, to a non-crystallizing sealing glass adaptable for sealing a glass panel and a glass funnel of a cathode-ray-tube (CRT) such as a color television tube.
As a sealing glass for the glass panel and the glass funnel of the CRTs, the crystallizing glass of the PbO--B.sub.2 O.sub.3 --ZnO--SiO.sub.2 type which is disclosed in British Patent No. 863500 has been known. The known sealing glass can be crystallized within a period of one hour at 450.degree. C. Since the known sealing glass has an elevated melting point after crystallization, it can provide a heat resistant seal. Accordingly, when the sealed bulb is again heated to the temperature between 350.degree.-400.degree. C. for an evacuation process during CRT production, the off-set between the panel and the funnel will not occur.
Therefore, the known crystallizing glass is preferable for the production of CRT bulbs which are subjected to a heat cycle after the sealing process.
Recently, the evacuating method has been improved so that evacuation can be carried out at a lower temperature than before. Therefore, the seal need not have the high heat resistance so much as before. On the contrary, it is required for the sealing glass to be possible to form a seal at a low temperature for a short time from the view points of a reduction in consumed energy and economization of the production.
However, the known crystallizing sealing glass requires to be fired, depending on the bulb size, at 440.degree.-460.degree. C. for 30-60 minutes in order to obtain the perfectly crystallized seal.